1. Technical Field
The present invention relates to photonic logic gates, and more particularly, to an EIT-based photonic logic gate that is tunable in bandwidth.
2. Description of Related Art
Photonic crystals are artificial periodic structures with photonic band gaps, and work by interacting with light. A photonic band gap of a periodic structure refers to a certain frequency range and any waves in the frequency range are not allowed to propagate in the periodic structure. The presence of band gaps promises photonic crystals prospects of extensive applications, because larger band gaps mean a broader band of adjustable light. When a photonic crystal is finished, its band-gap structure is fixed and its refractive index becomes unchangeable. Thus, when a different refractive index is needed, the only way is to make another photonic crystal with the desired refractive index.
While photonic logic gates have been discussed in some researches as recited below, one with a tunable band is still unknown.
As disclosed in E. Forsberg, J. She, Optoelectronic Materials and Devices (edited by Y. H. Lee, F. Koyama and Y. Luo, 2006), Proc. of SPIE 6352 (2006), 63520S, a lump of material incorporating therein with a piece of circular dielectric material that contained gaseous EIT (electromagnetically induced transparency) was set in the air for the purposes of research on potential approaches to materials with negative refractive indexes.
In S. Sangu, K. Kobayashi, A. Shojiguchi and M. Ohtsu, Phys. Rev. B 69 (2004) 115334, the study was directed to the probability of a CuCl-based material among 3 quantum dots being close to a light field, and use of the material after properly configured as an optical AND gate or XOR gate.
On the other hand, a CuCl-based material in 3 quantasomes (with a particle size ratio thereof being 1:2^1/2:2) was placed in a NaCl-material array for investigating into the transfer of near-field energy, as described in T. Kawazoe, K. Kobayashi, S. Sangu and M. Ohtsu, Appl. Phys. Lett. 82 (2003), 2957. The paper also proposed the use of the material in a nanoscale photonic switch.
In view of this, how to modify the internal geometric configuration of photonic crystals so as to change the external optical properties and in turn adjust photonic crystals in band would be an issue for the industry to address.